102	EDUCATIONAL PSYCHOLOGY
that if we think of the surplus energy as psychical rather than
physical the theory can be restated in a more convincing way.
Of great educational importance is the practice theory of
play, first suggested by Malebranche, and later developed and
defended by Karl Groos in his two works. The Play of Animals
and The Play of Man. Considering first the less complex pheno-
menon of play in the animal world, he notes that it is the
higher, not the lower animals that play. Higher animals, such
as the cat and dog, are helpless when born, and have a period
of immaturity during which they are dependent on then-
parents for protection and the provision of the necessities of
life: this period they utilize for play. Lower animals, on the
other hand,, such as the ant and the bee, are from the start per-
fectly adapted to their surroundings; they fend for themselves
straightaway, and spend no time whatever in frivolity. Groos
notes further that the form of play in the higher animals antici-
pates the serious activities of their adult lives: thus the kitten
in its play chases any moving object, so perfecting itself in the -
art of catching mice* The puppy, too, plays at fighting, so
practising an art that will stand it in good stead later on. He
concludes that the essence of play is its biological utility; he
^sees in it the exercise of instincts before they are needed for
serious use, such exercise leading to the skill that will be neces-
sary in the future. Play is ideological, always anticipating the
future needs of the animal.
Such a theory is highly plausible. Groos seems to be correct
in viewing helplessness at birth, a period of immaturity, and the
impulse to play as different aspects of a single phenomenon.
His argument is strengthened by the additional consideration
that the higher the position in the scale of intelligence to which
the animal ultimately rises, the longer is the period of imma-
turity accorded by Nature, and the more pronounced is the im-
pulse to play. Now we have seen that intelligence depends on
the degree to which the instincts are plastic: those animals,
such as the bee, that are born with stereotyped modes of re-
action in virtue o£ which they are perfectly adapted to their
environment throughout life, behave on an instinctive rather
than an intelligent level. But the plastic instincts, which are the